Apparatus for reducing ores and melting metals by electromagnetic induction



Oct. 3, 1944. c. Q. PAYNE 2,359,573

APPARATUS FOR REDUCING .ORES AND MELTING METALS BY ELECTROMAGNETICINDUCTION Filed Dec. 2, 1942 2 tsheet 1 I INVENTOR CLARENCE Q.PAYNE Oct.3, 1944. c. Q. PAYNE 2,359,578

APPARATUS FOR REDUCING ORES AND MELTING METALS BY ELECTROMAGNETICINDUCTION Filed D 2, 1942 2 Sheets-Sheet 2 INVENTOR cm/zz/vci Q PA YNETTRNE Patented Oct. 3, 1944 A UNITED STATE PATENT OFFICE 1 mana'rus FoaREDUCING oaEs .AND mama METALS BY ELECTROMAGNET- IC INDUCTION ClarenceQ. Payne, New York, N. Y. Application December 2, 1942, Serial No.467,608

4 Claims.

are electrically conductive or magnetically permeable, and which can,therefore, be internally heated by means of alternating electriccurrent. The invention is especially available for the treatment offinely divided ores, such as flotation concentrates, or ores whichrequire fine crushing to unlock them from their gangue minerals. Forsuch material close temperature control is desirable and is hereinprovided by means of rheostat control of the current in the primarycoil, in order to adapt it to a variety of ores.

This invention consists essentially in so combining an alternatingcurrent electromagnet with an induction furnace that the charge of thelatter forms the central core of the electromagnet. It also comprises soshaping the charge that its lower portion diminishes in volume whereby,with a reducing agent, it may be progressively reduced, at a lowtemperature and continuously discharged from the bottom of the furnacewhile the upper portion is absorbing heat by contact radiation from thelower portion, as well as from electromagnetic induction within thecharge itself. The same type of furnace may also be used at a highertemperature for melting a reduced product like sponge iron, to pureingot iron.

Instead of providing an electromagnet as shown in my Patent No.2,281,170 with a single magnetic flux circuit, and then causing a strongflux condensation at the coned end of the crucible charge, I find itadvantageous to provide the electromagnet with a dual flux circuit andto give each a strong magnetic "edge" condensa tion at the restrictedflat bottom of the charge.

- derstood from a description of the accompanying The rapid reversals ofthese flux condensations K by the alternating current greatly assist inheatingthechar'ge. I

An important andnovel feature of my present invention is tocause thecharge to move down- -'ward by its own weight as it passes through a"shell" type of windings; that is, they are concentric with eachotherand the'magnetic fiux circuit is on the outside of the windings.The secondary coil is given a load circuit 'by causing its terminals toclose through the'furnace charge. e v The nature of the invention willbe better unpart a rapid vibrating motion to the ore charge a while itis undergoing reduction or melting.

Figure 3 shows in vertical cross-section the electromagnet so combinedwith an induction furnace that the core of the electromagnet forms thecharge of the furnace.

Figure 4 shows in sectional view along the plane 4-4 of Figure 3 themagnetic edge concentrations of the lines of force in the dual fluxcircuits at the bottom of the furnace charge.

Figure 5 shows in sectionalwiew on 'the line 5-5 of Figure 3 therefractory sliding gate which controls the discharge of the reducedproduct from the furnace. V

Figure 6 shows a top view of the gate along the line M of Figure 5. 1

As heretofore designed practically all induction furnaces are providedwith an iron core in which the magnetic flux is generated by theelectric current in itsprimary winding. The magnetic flux is thentransformed by induction into a. high amperage current in the secondarycoil (which consists of the ore charge, or metal, sur-- v rounding thecore) and is converted into, heat by the magnetic reluctance of thelatter. design involves certain disadvantages which increase withthesize of the furnace; Here the distances which separate the primary andthe secondary coils .cause considerable magnetic leakage and thisinvolves a hight power loss.

-In my present induction furnace, on the other hand, I utilize part ofthe ore charge (which is given a'tape'ring shape as shown in Figure 3)as the core of the electromagnet in which to generate the magnetic flux.The ore charge. which is given a downward movement through the furnaceby its own weight, will have aconsiderably greater magnetic reluctancethan that of an iron core, due to the lower permeability of its materialand to the finely divided state of its particles. This reluctance showsitself in greater hysteresis losses and in eddycurrents than would bethe case in an iron core, and these rapidly develop This 'electromagnet.

a high temperature in the charge. This design thus secures part of thefurnace heat directly instead of wholly by transformation. The remainderof the path of the dual flux circuit, outside the core, as shown at [3,l4, l5 and I6 in Figure 3 is carried by laminated transformer iron whichhas a high magnetic permeability and low magnetic reluctance. Theirdimensions are also made ample in order to avoid any appreciabletemperature rise due to the flux reversals of the current which theycarry. There remain only the small air-gaps in the flux circuit shown attop and bottom of the crucible furnace in Figure 3. The entire length ofthe circuits as shown in Figure 3 is approximately as follows:

Per cent Two divided iron paths, each 61.0. One central core 30.0 Twodivided air-gaps, each 9.0

It will be evident from the above that the magnetic permeable portion ofeach flux circuit amounts to 91.0% of thewhole. Only enough airgaps'havebeen provided in these flux circuits to enable the crucible to beremoved for repairs and replaced at such intervals when it may becomenecessary. In this way the magnetic leakage is quite small and the powerfactor and efficiency of reduction should therefore be quite high.

Since the ores and minerals to be treated in this furnace will varywidely in their magnetic permeability, and since some of them lose theirmagnetism at high temperatures, there is provided as a safeguard inreaching a sufiiciently high temperature in the core, a secondary coilas shown at [2 in Figures 3 and 4. This consists of a few turns ofcopper tubing insulated when used thereafter for high grade steelalloys.

Hydrogen is undoubtedly the purest of the Various reducing gases anddoes not introduce any impurities in the reduced sponge iron. While thisgas may be applied under pressure to my furnace by providing suitableopenings in the lower part of the crucible l0, yet there are certaindifllculties, or objections, to the use of gas for this purpose. In thefirst place, itis more expensive for the same amount of reduction than asolid rewith asbestos tape on the outside and water cooled on theinside. This secondary coil encircles the lower part of the crucible. Itserves to transform or stepup the amperage of the primary coil. Thisgives it great heating value.

Moreover, to provide a suitable 'load in this cir-- suit, the terminalsof the secondary coil are made to close through the lower part of thecharge as 4 goes only partial reduction. As it gradually descendsthrough the crucible its volume is reduced I until it reaches thehighesttemperature zone of reduction or melting. The crucible is open atits lower end and rests in a refractory support 30,

Figure 3, which is held to the lower yoke of the This support contains asmall supply of the reduced material and below it a regulating, orcontrol, gate which maintains the charge in motion at a desired rate ofdischarge trol the temperature.

of the finished product, by varying the amount of the opening, as shownin Figures 5 and 6.

The objectof this invention is not only to reduce iron ores, especiallytheir oxides, with a reducing agent to sponge iron at a low tempera-.

ducing agent like carbon, in the form of coke, coal, or charcoal. Italso involves in this case greater difiiculty in the accurate adjustmentof the right amount of gas for the efficient reduction of thecountercurrent moving column of ore. By overcoming thedifiiculties-which have been associated with the use of carbon in thereduction of iron ores in.other reducing furnaces, it' is possible toutilize carbon for low temperature reduction of iron ore to sponge ironin my induction furnace and to thus attain a notable economy in theoperation of the furnace.

In rder to illustrate the great reducing power .of carbon, we may take ahematite ore which we will assume contains 55% metallic iron. Whenraised to the temperature of reaction, the equilibrium equation is thenas follows:

From this it is seen that along ton (2240 lbs.) of hematite orecontaining 55% iron, will require only 198 lbs. of carbon to reduce the1232 lbs. .of metallic iron which is present in the ton of crude ore.Since the carbon may be derived from coke or coal, which usually containabout carbon, the reduction will actually require 220 lbs. of coal forthe complete reduction. With coal at $5.00 per (short) ton this willrepresent a fuel cost of only 0.55

cent per ton of the 55% hematite ore. The heat derived from this smallamount of carbon is required only for the chemical reaction of thereduction. A certain amo'unt'of additional heat is also required tostart the reaction and to con- This is obtained by electromagneticinduction from the electromagnet as shown in Figure 3. This internalheat reacts only with the ore particles and not at all with'the gangueparticles nor with the coke or coal of the furnace charge.

Care should be taken in the use of carbon in my furnace for thereduction of th iron oxides (instead of hydrogen) to prevent temperaturerises higher than 900 C. It is, however, quite important to maintain theaverage temperature of the reduction at about 900 C. in order to preventsintering of the ore particles, and introducing impurit es into thesponge iron produced. This can be done by the following steps.

1. When the amount of carbon used is limited to that needed for theactual reduction of an iron ore, as in the case of the 55% hematitemenquired. This is crushed to about the same degree of fineness as theore particles themselves and is intimately mixedwith them.

2. The iron ore reduction. is an endothermic reaction and absorbsconsiderable heat. Since the ore and its gangue comprise 90% of thecharge, the coal particles are widely separated; the preponderating oreparticles will tend to reduce the temperature more than the coalparticles will tend to increase it above the 900 C. limit desired. Itis, therefore, necessary to supply an outside source of heat to maintainthe right heat level. This is derived from electric induction heat ashere explained. v

3. The heat thus availed of is internal heat and acts only on the oreparticles and not on the gangue particles in the ore. It also acts fromwithin outward, and the-amount of heat sup lied is under close rheostatcontrol, as shown in Figure 3. The absorption of carbon when in contactwith coarse iron particles forms iron car.

bide quite slowly. In my furnace the small size of the ore particles,their intimate mixture with the coal particles, and their rapidvibration cause the reduction to proceed through innumerable contactpoints and through the gas phase very rapidly. In this way it ispossible to keep the carbon limit in the sponge iron down to 0.10% to0.20% and thus make it available for high quality steel alloys, as wellas for other uses.

The operation of the furnace will be quite clear from the abovedescription of the principle on which it is designed. From Figures 1 and2 it will be seen that the base of the induction furnace is mounted onan angle-iron frame l1, It, provided with an end extension whichsupports vertically adjustable bearings and a shaft. These carry theflywheel 20. The flywheel is driven by a belt from the motor 2|, placeddirectly below it. Adjustable weights placed close to the rim of theflywheel enable it to be thrown out of balance and thus to develop avariable amount of centrifugal force. The frame l1, l8 and the furnaceattached to it ar supported on rollers I9 which rest on the table top22. When the motor is in operation it revolves the flywheel at a speedof about 1800 R. P. M. and the centrifugal force of the flywheel impartsa minute but very intense oscillation, or vibration, to the frame andthrough it to the ore particles in the crucible of the furnace, withoutany direct mechanical connection between the motor and crucible. Thisactive vibration of the ore particles greatly assists in the reductionof the ore to sponge iron by constantly presenting new points of contactbetween the ore and coal particles, as they move actively amongthemselves, and in the steady downward movement of the charg through thecrucible. It also assists the CO: gases to move upward .while thereduced sponge iron moves downward, and tends to prevent sticking of theheated particles to the crucible walls. It thus increases the capacityof the furnace by reducing the time required for reducing the ore tosponge iron.

The heat required for equalizing and maintaining the ore charge at atemperature of about 900 C. is obtained from alternating electriccurrent by induction from the primary H and secondary fleld coil II,which are placed concentrically around the ore charge in the crucibleID, of Figure 3. The electromagnet is preferably designed with a dualmagnetic flux circuit as shown by the broken lines in Figure 3. Each ofthese flux circuits is given an intense edge concentration of themagnetic flux, as shown in Figure 3, and diagrammatically in plan viewin Figure 4 at I02. These assist in creating an intense local heatingzone at the bottom of the crucible, as the charge moves progressivelythrough it. As a further safeguard in securing a high limit oftemperature, for melting certain reduced ores, I also make use of a loadcircuit of the induced current from the secondary coil by causing thterminals of the secondary coil to be closed by the lower part of thecharge in the crucible as shown at A-IB in Figure 3, where the addedheating eifect will be most effective.

The lower end of the crucible I0 is open and rests upon a highlyrefractory support 30 which contains a horizontal sliding gate which isoperated by a shaft 32 and hand wheel 33, Figure 2. The opening andclosing of the gate, on which the rate of discharge depends iscontrolled by a suitable screw on the shaft 32, which is revolved in thefixed bearing 34.

When the reduced ore, as sponge iron, is discharged from the furnace itis made to fall upon inclined water cooled plates 40, ll, in order tochill it quickly and to prevent reoxidation. These plates are attachedby flanged cheekplates to the bottom of the furnace frame l1, l8, andvibrate with it. They, therefore convey it downward until the spongeiron falls into the receptacle 42. This cooled sponge iron is then putthrough separators to remove the nonferrous material from the spongeiron concentrate, and

' is then utilized for the variouspurposes to which it is adapted. If itis desired to melt the sponge iron to ingot iron, the cooling plates 40,4| are omitted and the temperature of the furnace is raised to about1500" C. The molten sponge iron as it is discharged from the furnace isthen allowed to fall into ingot molds and to cool very slowly so that itwill retain its low carbon softness, which makes it very desirable forvaried steel alloy use.

This furnace although designed primarily for J the reduction and meltingof iron ores, may also be utilized for certain nonferrous ores eitherfor reduction or melting. The above description is therefore merelyillustrative and it is understood that modifications may be made withoutdeparting from the spirit of the invention as defined in the appendedclaims.

Iclaim: Y

1. Apparatus for reducing finely divided iron ores which includes avertical alternating current electromagnet having a dua1 magnetic fluxcircuit and an induction furnace whose c arge forms the continuouslydownward moving core of the electromagnet; means for raising the lowerend of said core-charge to a higher temperature than its upper end;means for vibrating said charge, in combination with means forcontinuously removing the reduced material from the bottom of thefurnace through a refractory regulating gate.

2. Apparatus for reducing finely divided iron ores which comprises thecombination of a vertical alternating current elect'romagnet and aninduction furnace whose moving charge forms the central core of theelectrc'magnet; means for Y transforming the amperage of the fluxcircuit of the' primary coil into a higher amperage in that of thesecondary coil, and means for utilizing the heat of the load circuitdeveloped by induction core forms the downward moving ore-charge of thefurnace; a secondary coil placed concentricaily with the primary coiland with the central I ore-charge of the electromagnet; means forpassing two magnetic flux-circuits generated by the primary field coil,through the central ore charge; in combination with means for raisin thetemperature of the ore-charge to the reducing point, by concentrationsof the flux densities at each of said flux circuits at. the lower end ofsaid ore-charge, and means for vibrating the ore charge. CLARENCE Q;PAYNE.

